After the Rebellion, the animals start to live according to Old Major's philosophy: "From each according to ability, to each according to need." Ideally, this would mean that every animal has an equal share of the food in the amounts necessary to keep them alive and healthy. Milk from the cows, which is a luxury for animals other than calves, should be apportioned equally as a treat. However, the pigs take all the milk, and all the windfall apples, for themselves. This is an early sign of their eventual exploitation of the farm, but Squealer is able to convince the animals that the unfair distribution is necessary:
"Our sole object in taking these things is to preserve our health. Milk and apples (this has been proved by Science, comrades) contain substances absolutely necessary to the well-being of a pig. We pigs are brainworkers. The whole management and organisation of this farm depend on us... Do you know what would happen if we pigs failed in our duty? Jones would come back!"
(Orwell, Animal Farm, msxnet.org)
Squealer makes two appeals here: one to authority and one to fear. His claim that "science" has proved that pigs need milk and apples to stay healthy cannot be verified, but it sounds plausible, and more importantly it sounds smart. The animals can't contest it because most of them can't read. He also appeals to fear, claiming that if the pigs fail in their organizing, Jones will return. This is demonstrably untrue as Jones tries and fails to take the farm back, but the fear is enough to quell opposition.